Nuclear power is back. As temperatures rise, fission is starting to look green compared with fossil fuels.

Companies like NRG Energy Inc. are seeking to build the first U.S. nuclear reactors in three decades, and environmental activists are embracing as clean and safe the technology they once vilified.

Gwyneth Cravens, a novelist and former anti-nuclear protester, is one of the technology's new apostles. In ``Power to Save the World,'' she takes a journey through America's nuclear heartland, from the New Mexico Mining Museum, with its display cases of uranium ore chunks, to the belly of Nevada's Yucca Mountain, still waiting for loads of radioactive waste to bury.

Cravens's guide and hero is a retired Sandia Labs chemist named Rip Anderson, who introduces her to all the right nuclear folks: marine biologists and epidemiologists, physicists and doctors.

Making electricity from nuclear power, writes Cravens, produces a tiny fraction of the greenhouse-gas emissions that coal, gas or even solar-based systems do. The accidents at Chernobyl and Three Mile Island also led to new plant designs with more safeguards -- though it's still unnerving to read that Chernobyl was a badly designed plant with poorly trained workers. Sloppy workplace habits tend to be the rule, not the exception.

Bad Science

Still, worries about cancer and mutations from widespread radioactive contamination, Cravens says, are based on bad reporting of bad science.

Chernobyl, for instance, caused no significant increase in overall cancer rates, according to 2005 findings jointly presented by several groups, including UN agencies and the World Health Organization. (Childhood thyroid cancers did increase, however, with approximately 4,000 cases diagnosed after the accident -- a circumstance Cravens glides over.)

The Chernobyl meltdown exposed people in neighboring parts of Russia, Ukraine and Belarus to an average of 490 millirems of radiation a year. (Millirems measure absorbed radiation.)

By comparison, one round-trip continental U.S. flight yields about 3 millirems of radiation, while an X-ray accrues 10 and smoking two packs a day for a year racks up 16,000. Annual radiation from the earth itself is 240 millirems. Nuclear plants give nearby residents less than 1 millirem per year.

Good Science

These figures are a revelation, putting nuclear energy back into play as a less than terrifying option. Cravens also assures us that disposal of waste has been thoroughly studied and tested (highly radioactive spent fuel can be safely buried underneath dry New Mexican salt beds or deep beneath the sea floor), and that power-plant fuel is extremely difficult to convert into weapons-grade material because of the reprocessing it requires.

Despite Cravens's detailed explanations of radioactivity and risk, often via monologues from Anderson, her trip to the nuclear netherworld turns off-puttingly zealous. She's so eager to pin salvation on nuclear power that she places every sentence at the service of her new agenda.

She writes of a ``beautiful, limpid blue'' spent-reactor- fuel pool; of a ``tastefully landscaped'' nuclear-plant visitor center; of underground caverns into which spent fuel is remotely loaded by enthusiastic, perfectly trained workers.

Cravens doesn't talk to detractors: Hysterical activists (including herself in her past life) serve as loony straw men.

There are, of course, respectable dissenters, such as Amory Lovins, chairman of the Rocky Mountain Institute, who argues that creating and distributing nuclear energy is too slow and too expensive. More defensible choices, according to Lovins, include micropower based on wind, solar and geothermal sources and increased efficiency.

Cravens's impassioned defense of nuclear power raises as many questions about how to meet energy demands as it answers. That's a good start.

``Power to Save the World: The Truth about Nuclear Energy'' is published by Knopf (464 pages, $27.95).

(Carly Berwick writes for Bloomberg News. The opinions expressed are her own.)